Template-Free Synthesis of Ruthenium Oxide Nanotubes for High-Performance Electrochemical Capacitors

One-dimensional, hydrous ruthenium oxide nanotubes (RuO2·1.84H2O) have been successfully achieved using a template-free, microwave-hydrothermal process. These were found to be amorphous in nature and have a large specific surface area of 250 m2·g–1, producing a specific and volumetric capacitance of 511 F·g–1and 531 F·cm–3, respectively, at a discharging current density of 0.5 A·g–1. When used as an electrode material in an electrochemical capacitor or ultracapacitor, they produced a significant improvement in capacitance, rate capability, and cyclability that can be attributed to the hollow nature of tubes allowing greater contact between the active surface of the electrode and the electrolyte.